1. Field of the Invention
This invention relates to a commercially advantageous process for the production of 2,3-dichloropropionitrile. More specifically, this invention pertains to a process for the production of 2,3-dichloropropionitrile by chlorinating acrylonitrile with chlorine in the liquid phase in the presence of pyridine or an alkylpyridine in combination with an alkaline earth metal carbonate.
2. Description of the Prior Art
2,3-Dichloropropionitrile is an industrially useful compound that finds application as a raw material for polymeric compounds, amino acids, agricultural chemicals, medicines, etc.
A usual process for the production of 2,3-dichloropropionitrile comprises blowing chlorine gas into a liquid phase containing acrylonitrile in the presence of a catalyst, and purifying the resulting reaction mixture by distillation. Inorganic catalysts such as sodium bicarbonate and sodium hydrogen phosphate or organic catalysts such as pyridine, quinoline and dimethyl formamide are known as catalysts useful in this process. In commercial practice, the use of an organic catalyst, especially pyridine is advantageous.
Production of 2,3-dichloropropionitrile by the chlorination of acrylonitrile in the liquid phase using pyridine as a catalyst is described, for example, in Angew. Chem., A, 60, 311 (1948), Zhur. Obshch. Khim, 28, 139 (1958), and Journal of Organic Chemistry, 26, 2324 (1961).
These known processes, however, give rise to various problems in commercial practice because unless expensive pyridine is used in an amount of as large as about 15 to 30% by weight based on acrylonitrile, an abrupt exothermic phenomenon occurs and 2,3-dichloropropionitrile cannot be obtained. For example, according to the known processes, pyridine is present in a high concentration in the reaction solution after the reaction, and therefore, distillation by heating of the reaction solution as obtained results in the dehydrochlorination of 2,3-dichloropropionitrile. If, in an attempt to prevent the dehydrochlorination reaction, the reaction solution is washed prior to distillation to remove pyridine, a part of the 2,3-dichloropropionitrile together with the unreacted acrylonitrile dissolves in the water layer, and the yield of 2,3-dichloropropionitrile is reduced. An additional serious problem is that the disposal of the waste water which gives off an offensive odor by the inclusion of pyridine becomes difficult.
It is an object of this invention therefore to provide a novel process for the production of 2,3-dichloropropionitrile, which is industrially advantageous in that the amount of the pyridine-type catalyst used is extremely small and the reaction solution needs not to be washed with water before distillation.
The present inventors have found that if a specified amount of an alkaline earth metal carbonate is used together with pyridine or an alkylpyridine in the above process, the amount of the pyridine or alkylpyridine used can be drastically reduced without a decrease in the yield of 2,3-dichloropropionitrile as compared with the known processes in which pyridine is used alone.